* The research reported herein was performed by the Arnold Engineering Development Center (AEDC), Air Force Materiel Command. Work and analysis for this research were performed by Sverdrup Technology, Inc., AEDC Group, technical services contractor for AEDC; SY Technology, Inc., Huntsville, Alabama; and WaveFront Sciences, Albuquerque, New Mexico. Further reproduction is authorized to satisfy needs of the U. S. Government. # Associate Fellow, AIAA + Senior Member, AIAA ABSTRACT A series of aero-optics tests have been carried out at Mach 7 in the Hypervelocity Wind Tunnel 9 (Tunnel 9) at the Arnold Engineering Development Center (AEDC). The test-bed used for the measurements were two flat plates which had sapphire windows mounted in titanium frames. Aero-optic measurements included near-field phase and intensity measurements made with two wavefront sensors, farfield point spread functions made with an imaging camera, and high frequency optical tilts (bore sight error) made with an X-Y Detector. Ancillary measurements of pressure and heat transfer on the testbed plates were also made. The aero-optic measurements coupled with a variety of computations resulted in phase and intensity maps, bore sight errors, contained energy diameters (CED’s) and point spread functions (PSF’s). Comparisons between the various measurements are made to ascertain aerodynamic effects, instrument errors, facility-induced errors and measurement uncertainties.

Missile interceptor seeker windows undergo significant heating and stress during supersonic flight. These effects lead to window and flow field distortions that can significantly degrade the image quality on the seeker. We have applied a ShackHartmann wavefront sensor for measuring these effects in ground test. The Shack-Hartmann sensor measured the near-field intensity and phase distribution. Because these distributions are linear, relative (or flow on/flow off) measurements can be made where test instrumentation errors can be subtracted out. The image quality, or point spread function, can be computed from these near field measurements. This allows for measurement of the aero-optic quantities that are a simulation of flight conditions, and an accurate prediction of sensor end-to-end performance. In making point spread function predictions, it is first necessary to establish that the near-field measurements have sufficient accuracy and resolution. To this end a laboratory experiment was constructed that allows direct comparison between measured point spread function and wavefront sensor based predictions. Excellent results were observed with strong, high spatial frequency aberrations. The wavefront sensor was then applied to make measurements in supersonic flow. Tests have been conducted of simulated seeker windows at Mach 7 and 8 conditions, and time-resolved wavefront sensor measurements have been made in some conditions. While early results have significant facility induced vibration in some conditions. Nevertheless, aero-thermal window heating has been observed in low stress conditions.